In general, a container is a kind of transport container which is a standardized box that can carry a large quantity of cargo for land transportation or shipment transportation and refers to a box for transporting cargo safely and conveniently. The container is also standardized receiving equipment for a bulk cargo.
Containers are transported on container vehicles on land, and at sea, a large number of containers are transported using large container carriers to load containers.
A vehicle called trailer is used as a means of transporting the container by land, wherein the trailer which is without a driving power device or a control device is generally pulled by a tractor.
The trailer is designed to fit the size of the container so that a standardized container can be loaded, and is designed considering the weight of cargo loaded in the container. The trailer loads one or two containers, and in order to prevent the container from separating from the trailer in case of sudden braking, curved roads, slope, and other unexpected situations that occur during transportation, a locking device for locking the container is provided at the upper portion of the trailer.
The use of the locking device has been systematically mandated and prior art of manual or automatic methods have been proposed.
FIGS. 1a and 1b are sectional views showing a manual locking device according to the conventional art before and after operation.
As shown in FIGS. 1a and 1b, the manual locking device according to the conventional art is configured such that a lock 2 performing locking or unlocking functions by rotation and up and down movement of a lever 3 is provided at multiple locations of an upper frame 1 provided in a trailer, whereby as a driver manipulates the lever 3 of the lock 2 with the container 4 mounted at a predetermined location of the upper frame 1, a head part 2′ provided at the upper portion of the lock 2 is inserted into and engaged with a coupling hole 5 formed in a lower surface of the container.
In other words, the manual locking device allows the trailer and the container loaded thereon to be integrally coupled together, thereby providing stability during transport.
However, since the locking device is cumbersome in the state where the container is loaded, most drivers do not operate the locking device. In particular, when driving on poor roads or rough curves without locking the container, a major accident, such as a container separating or falling from the trailer, may happen.
To solve the above problem, an automatic locking device has been disclosed in the document of Korean Utility Model Registration No. 20-0186762.
FIGS. 2a and 2b are sectional views showing an automatic locking device according to the conventional art before and after operation.
As shown in FIGS. 2a and 2b, the automatic locking device according to the conventional art includes: an actuator 20 having a hollow portion 21 provided in a cylindrical housing 10 mounted to an upper frame of a trailer, and configured to be moved upward by an elastic force of an elastic spring 22 and an external load; a lock 30 including a head part 31 provided coaxially with the hollow part 21 of the actuator 20 and inserted into the container, and a stop protrusion 32 operation in conjunction with the operation of the actuator 20; a slit groove 41 with a curved surface formed in a groove 40 having a predetermined depth formed in the lock 30, and configured to induce the lock 30 to be rotated to a predetermined range when moved down; a support shaft 50 fixedly provided in a cover 11 coupled to a lower surface of the housing 10 to freely slide in the groove 40 by means of an elastic spring 52; and a pin 51 provided on an upper outer circumference of the support shaft 50, and configured to displace a direction of the lock 30 that is moved up and down along the slit groove 41 based on a location, as a fixed axis, where the pin is inserted into the slit groove 41.
In other words, the automatic locking device automatically performs locking and unlocking functions by the weight of the container in the process of loading or unloading containers, whereby it is possible to transport the heavy container while safely locking it, and is possible to prevent inconvenience caused by the operation of the lock.
However, the automatic locking device according to the conventional art is problematic in that when locking and unlocking functions are not normally performed due to malfunction of the components, the locking device is disassembled and dismounted from the trailer, and then replaced with a new locking device.
The automatic locking device is further problematic in that a horizontal impact load is applied to the container due to rapid operation of the trailer, sudden braking, sharp curves, etc. At this time, the impact is directly applied to the lock and the hollow portion coupled to the container and the actuator, whereby durability is degraded due to damage to the components coupled with the lock, which causes malfunction.
Meanwhile, containers are loaded or unloaded on trailers using dedicated devices or forklifts. Here, the head part of the lock may not be correctly inserted into the connector of the container and be displaced. In this case, the load of the container is transferred to the head part of the lock rather than the actuator, and thus the lock is vertically moved down without being properly inserted into the connector, whereby the components coupled with the lock may be damaged, and engagement may not be performed easily.